| ard 
1877.) 217 (Smith. 
beaker and evaporated ; water then added and the solution filtered. The 
residual, unattacked mineral powder after washing, drying and igniting, 
weighed .0820 grms. The filtrate from this was treated precisely as in (1) 
and the chromium oxide obtained from it amounted to 28.05 per cent. 
III. In this experiment only .1500 grms. substance were employed. The 
material was of the same fineness as in (II). Instead of using dilute bro- 
mine water as heretofore, an excess of bromine was poured over the sub- 
stance and but a very small quantity of water added. For three days the 
tube was exposed to a temperature varying from 150° - 175° C. At the ex- 
piration of this time the tube was examined, and as the substance appeared 
to be perfectly decomposed, the solution was removed from the tube and 
evaporated in a beaker glass to expel the large excess of bromine, upon the 
gradually disappearance of which a dark powder showed itself. The solu- 
tion was strongly diluted with water and filtered. The insoluble residue 
was thoroughly washed with hot water. Dried and ignited, this weighed 
_.0140 grms. 
The filtrate was mixed with an excess of ammonium hydrate and evapo- 
rated almost to dryness in a casserole. The solution was then diluted with 
water and filtered from the aluminum hydrate, &c., and treated as in (1). 
The percentage of chromium oxide extracted equaled 49.60 per cent. 
IV. From the preceding experiments it appeared very evident, that all 
that was lacking to render the decomposition complete was to have the 
chromic iron in an exceedingly fine condition. To this end the material that 
had been ground to an impalpable powder in an agate mortar was elutri- 
ated, then drted, and two separate portions of .1500 grms. each placed in 
good, hard glass tubes. To each portion was added a rather large quantity 
of bromine water and from 10-12 drops of bromine. Both tubes were 
heated for one day at 130° C. For two successive days the temperature. 
was maintained at 170° C. At the expiration of the third day, one of the 
tubes was removed from the oven and opened. Red oxide of iron had 
separated and undecomposed material was no longer visible. The whole was 
poured into a beaker and evaporated ; water added and filtered. The resi- 
due was thoroughly washed, dried and ignited, then transferred toa beaker 
glass and heated with dilute hydrochloric acid. The entire mass dissolved 
readily and without a residue. The decomposition was, therefore, com- 
plete. 
The filtrate from the ferric oxide was evaporated almost to dryness after 
the addition of an excess of ammonium hydrate, then diluted and filtered. 
The solution was reduced with hydrogen sulphide and the precipitate, after 
filtering and washing, dissolved in dilute hydrochloric acid and re-precipi- 
tated with ammonium hydrate. This operation was repeated and the chro- 
mium oxide obtained was 62.66%. 
The second tube which was removed not long after the first, contained 
a large amount of separated ferric oxide. This, after filtering off the chro 
mium solution, also dissolved very readily in warm, dilute hydrochloric 
acid, leaving not the least trace of residue. 
PROC. AMER. PHILOS. soc. xvit. 100. 2B. PRINTED JAN. 12, 1878. 
